1. Field of Endeavor
The present invention relates to sensors and more particularly, to a Fabry-Perot optical sensor.
2. State of Technology
Fiber optic sensors have a number of beneficial properties over conventional electronic sensors, such as operating in harsh environments, remote sensing, smaller construction, and because such devices are non-electrical, they are not subject to electromagnetic interference. Generally, Fiber optic sensors operate by encoding non-optical external perturbations onto an optical carrier. The design of such a sensor determines whether the external perturbation modulates the amplitude, phase, differential phase, or spectral distribution of the optical carrier.
Most fiber optic sensors are classified into two categories, intrinsic and extrinsic. Perturbations on an intrinsic sensor act on a fiber and the fiber alters characteristics of the internally guided light. An extrinsic fiber optic sensor has a separate device to alter the light. The fiber utilized as part of an extrinsic sensor package, merely acts as a means for getting the light to and from a designed sensor, such as, for example, a Fabry-Perot Etalon.
Background information on a commercially available fiber optic sensor based on a white light Fabry-Perot interferometric readout concept for measuring strain, temperature, etc., can be found on http://www.fiso.com. Such sensors are generally made by precisely positioning and attaching segments of optical fiber in tiny glass capillary tubes.
Additional background information on Fabry-Perot optical sensors can be found in U.S. Pat. No. 5,202,939 and U.S. Pat. No. 5,392,117, both by Bellville et al., issued Apr. 13, 1993 and Feb. 21, 1995 respectively, including the following information from the abstract of the U.S. Pat. No. 5,202,939, “The optical sensing device and the method thereof are for measuring a physical parameter. The device is to be connected to a light source which generates a multiple frequency light signal having predetermined spectral characteristics. The device comprises a Fabry-Perot interferometer through which the light signal is passed, an optical focusing device for focusing at least a portion of the light signal outgoing from the Fabry-Perot interferometer, and a Fizeau interferometer through which the focused light signal is passed. The Fabry-Perot interferometer includes two semi-reflecting mirrors substantially parallel to one another and spaced by a given distance so as to define a Fabry-Perot cavity having transmittance or reflectance properties which are affected by the physical parameter and which cause the spectral properties of the light signal to vary in response to the physical parameter. The Fabry-Perot interferometer is provided with at least one multimode optical fiber for transmitting the light signal into the Fabry-Perot cavity and for collecting the portion of the light signal outgoing thereof. The Fizeau interferometer includes an optical wedge forming a wedge-profiled Fizeau cavity from which exits a spatially-spread light signal indicative of the transmittance or reflectance properties of the Fabry-Perot interferometer. The physical parameter can be determined by means of the spatially-spread light signal.”
Accordingly, a need exists for an efficient manufacturing process to produce a novel rugged fiber optic sensor for measuring predetermined physical parameters. The present invention is directed to such a need.